Personal Video Recorders (PVR) have recently been introduced to the marketplace to permit digital recording of television broadcasts (whether over cable, satellite, or other broadcast technique). Such devices record television programming using a hard disc drive (HDD). A HDD generally has large memory capacity and is well suited for long recording time. However, HDDs have many disadvantages also. They are generally physically large, and thus an internal HDD requires a relatively large space. An external HDD occupies household space on the top or on the side of a Set-Top Box or TV set.
The recording density of a HDD is rising rapidly while the cost per bit or byte is simultaneously drastically falling. However, the low end of the total cost of a Hard Disc Drive may be limited by the need for a tightly sealed, durable case and a HDD interface. Additionally, by its mechanical nature, a HDD is vulnerable to mechanical shock and when damaged is not easy to repair. Since the HDD a mechanical device, it is usually the least reliable part in a television Set-Top Box or other digital television accessory. Also, replacement of a HDD may be complicated since, usually, the whole of the HDD unit has to be replaced. The limits of the mechanical seek time also limits the speed of certain trick play modes.
In addition to the above disadvantages, a HDD cannot generally be considered very secure since the interface (IDE, SCSI, iLINK) is normally a standard PC type interface. Thus, stored data can be easily read and pirated by connecting the HDD to a PC. This is a distinct disadvantage in an environment where conditional access is used to restrict viewing of copyright material to those who pay the appropriate fees. Although a HDD has many advantages, it is not an ideal storage medium for video recording.